A person has forgotten the last digit of a telephone number, so he dials the number with the last digit randomly chosen. How many times does he have to dial (not counting repetitions) in order that the probability of dialing the correct number is more than 0.5.

More than 5 times

Step-by-step explanation:

There are 10 options for the last digit (0, 1, 2 ... 9)

Probof 0.5 means 50% chance of getting it right,

Which would happen when he has tried 50% of the total possibilities, which are 10

50% of 10 = 5

He'll have to dial 5 times for a probability of 0.5.

More than 5 times for a probability of more than 0.5